It isn’t necessarily about intelligence, since stupid is as stupid does.
I tend to call that willful ignorance. It’s knowing that there are other ways of thinking, but refusing to even consider them. Which is stupid, dumber than dammit, and/or moronic. I’ve known some damn intelligent people that are stupid by virtue of not using their brain.
Be aware though, not everyone can control their volume. I don’t doubt you were aware of that, but it’s not so rare a thing as to not be worth mentioning. There’s also others that have trouble controlling volume.
Again, I don’t doubt you meant the folks that can control their volume, and do so without difficulty, just adding to things.